1. Field of the Invention
This invention relates to an armature core which is laminated with punched-off core sheets.
2. Discussion of Background
FIG. 5 is a sectional diagram showing an armature of a comparatively small-sized direct current machine for a vehicle and the like, provided with a conventional armature core. A reference numeral 1 designates an armature which is constructed as follows. A numeral 2 designates a rotating shaft, and 3, an armature core which is fixed to the rotating shaft 2, laminated with a number of core sheets 4 punched off from a steel sheet such as cold-rolled steel sheet or silicon steel sheet, on which surfaces no insulating treatment is performed. A numeral 5 designates an armature coil installed to the armature core 3, and 6, a commutator fixed to the rotating shaft 2, wherein the armature coil 5 is connected to a connecting portion 6b of a commutator bar 6a.
FIG. 6A is a front diagram of a conventional armature core, and 6B, a sectional diagram thereof. The core sheet 4 of the armature core 3 is formed with slots 7, an opening for shaft 8 and punched-out protrusions 9, on its top surface, which is formed by punched-in recesses 9a on the bottom surfaces of the core sheet, both by press-working. As shown in FIG. 6B, the press-worked core sheets 4 are continuously and successively laminated, and the protrusions 9 on the top surface of the core sheet 4 fit in the recesses 9a of the contiguous core sheet 4 on the bottom surface by pressing, thereby integrally laminating the core sheets. In this way, the core sheets 4 which have been punched off by the press-working step, construct the integrated armature core 3 by a succeeding laminating means. It is not necessary to laminate the core sheets after rearranging the respective punched-off core sheets 4. The laminated sheets are not disintegrated in the later steps.
In the conventional armature sheets 3, the respective core sheets 4 are laminated without clearance by fitting the protrusions 9 of the core sheet on the top surface into the recesses 9a of the contiguous core sheet on the bottom surface by pressing. Therefore, the respective core sheets 4 contact each other on the outer diameter face of the armature core 3, whereby the iron loss by eddy current is considerable, which lowers the output thereof.